Gold and nickel particles immobilized on alumina were prepared by the metal vapor synthesis and anionic adsorption methods. The dispersion of metals was determined by X ray diffraction and transmission electron microscopy. The activity of nanoparticles, tested in model catalytic reactions of CCl 4 addition to multiple bonds and allyl isomerization of allylbenzene, changes in a wide range (from 1 to 3000 (mole of product) (mole of Au) -1 h -1 ) and is parallel to the chromatographically measured heats of adsorption of the corresponding unsaturated substrates. The heat of adsorption of unsaturated hydrocarbons can serve as a criterion for the efficiency of the gold containing catalyst in olefin conversion.Nanosized gold particles possess high catalytic activity and selectivity. 1-11 Gold nanoparticls immobilized on oxide supports are highly active in the addition of carbon tetrachloride to multiple bonds 12 and in the allyl isomer ization of olefins. 13 Information on the strength and na ture of interaction of nanoparticles with reactants is nec essary for an understanding of the mechanisms of isomer ization and addition that occur on immobilized gold nanoparticles. Therefore, data on the adsorption of re agents and test molecules of different types are of great interest.In the present work, the heats of adsorption of carbon tetrachloride, allylbenzene, and oct 1 ene on nanosized particles of gold, nickel, and mixed samples Au + Ni were measured by chromatography. To reveal the contribution of alkyl chains, double bonds, and aromatic fragments of substrate molecules, alkanes and simplest aromatic hy drocarbons were chosen as test substances. The simplest homologue of CCl 4 , viz, chloroform, was taken to eluci date the contribution of the C-Cl bond to adsorption.
ExperimentalBenzene (Aldrich, 98%), allylbenzene (Aldrich, 98%), and oct 1 ene (Merck, 96%) were distilled over sodium. Halo substituted hydrocarbons, ethanol, alkanes, and triethylamine (all special purity grade, 98%) were used after drying and distil lation. All distilled samples, except for olefins, were stored above molecular sieves 4 Å (NaA).Preparation of catalysts by the anionic adsorption and metal vapor synthesis methods. Immobilized nano and ultradispersed particles were obtained by anionic adsorption and metal vapor synthesis. 12 Microspherical γ Al 2 O 3 (IKT 02 6M trade mark, AO Katalizator, Russia) with a specific surface of 138 m 2 g -1 was used as the support for nanoparticles. When the catalysts were prepared by anionic adsorption, chloroauric acid hydrate HAuCl 4 •xH 2 O (Aurat, TU 6 09 05 1075 89 trade mark) with the weight content of Au 49.04%, distilled water, and a 0.1 M solution of NaOH were used. A gold and/or nickel wire (l = 30 mm, d = 1.5 mm) was used as the metal source in the metal vapor synthesis. Determination of the average particle size by transmis sion electron microscopy (TEM) and X ray diffraction analysis. Electronic microphotographs of organosols Au-Et 3 N, Au-Ni-Et 3 N, and Ni-Et 3 N were obtained on a Jem 100 in stru...
